This invention pertains to rotary or angular position sensors which are both durable and precise for application in rugged and demanding environments, particularly for application with internal combustion engines as transmission selector position sensors. This invention further pertains to sensors that are designed to be integrated into an overall assembly such as a transmission assembly.
Automobiles typically use a gear shift lever to enable the driver to change gears in the car. This shift lever is mechanically linked to a selector shaft in the transmission. In an automatic transmission, the driver can typically select between Park, Reverse, Neutral, Drive and Low gear. Increasingly, automobiles are being equipped with electronic controls to control various aspects of the engine. One such control can be used in the control of the transmission.
An electronic control unit for the transmission needs an electronic indication of the position of the gear shift lever. Past designs have utilized an electro-mechanical switch that provides an indication of the position of the gear selector shaft. While these switches provide a relatively simple solution they are not ideal. They are required to be positioned remote from the transmission and can include significant cost.
Various alternative mechanisms can be used to sense the selector shaft position. One approach is to use a Hall effect sensor. This type of sensor incorporates a magnet with a varying magnetic field. The Hall effect sensor provides an electrical output that is proportional to the strength of the magnetic field surrounding it. As the magnet is moved around the Hall effect sensor, the output varies to reflect the change in position. By attaching the magnet to the shaft, it is allowed to rotate as the selector position is changed. The Hall effect sensor then senses this movement and provides an electrical signal representation of the position of the selector shaft.
The magnet and the Hall effect sensor must be kept in proper alignment with each other. If the magnet is allowed to move or to be positioned incorrectly, the output from the sensor will not properly indicate the position of the selector shaft. This is easily accomplished when the sensor and the magnet are provided in a complete assembly. However, when separate pieces are provided to a transmission manufacturer, the possibility for improper assembly is introduced.
It is therefore an object of the present invention to provide a transmission selector shaft position sensor that can be incorporated into a transmission housing easily and reliably. It is a further object of the present invention to provide the separate components in a single assembly. It is a further object of the present invention to provide the components of a transmission selector shaft sensor that may be quickly located and assembled into a transmission housing.